The present invention relates to improvements in methods of and in apparatus for changing the permeability of tubular envelopes or wrappers of rod-shaped articles of the tobacco processing industry. Such articles include plain cigarettes, cigars, cigarillos and analogous smokers' products of unit length or multiple unit length, continuous cigarette rods or the like, tobacco smoke filtering mouthpieces of unit length or multiple unit length as well as continuous filter rods.
It is well known to alter or adjust the permeability of wrapping material (such as cigarette paper or so-called tipping paper) for rod-shaped fillers which consist of or contain shredded tobacco leaf laminae, comminuted reconstituted or substitute tobacco, filter material for tobacco smoke and/or other constituents of rod-shaped smokers' products. It is also well known to select the permeability of such, wrapping material by resorting to adjustable devices which perforate the wrapping material, e.g., mechanically by employing needles or analogous implements, or by resorting to one or more lasers or other suitable radiation sources.
As a rule, a filter cigarette which is provided with an air-transmitting wrapper is permeable in the region of its filter mouthpiece so that, while drawing tobacco smoke from the lighted tobacco-containing portion of such article, the smoker simultaneously draws and normally or often inhales atmospheric air which enters through the perforations in the tubular envelope for filter material. Such mixing of tobacco smoke with atmospheric air in the interior of a filter cigarette exhibits numerous important advantages. Thus, the smoker inhales a smoke which contains less nicotine and/or tar, and the atmospheric air entering the filter cigarette through the perforations in the tubular envelope for filter material reduces the temperature of the column of smoke entering the mouth of the smoker.
FIG. 17 of U.S. Pat. No. 4,281,670 (granted Aug. 4, 1981 to Heitmann et al. for “APPARATUS FOR INCREASING THE PERMEABILITY OF WRAPPING MATERIAL FOR ROD-SHAPED SMOKERS' PRODUCTS”) illustrates a portion of a filter cigarette making machine wherein successive groups of three coaxial rod-shaped commodities (namely two plain cigarettes of unit length and a filter mouthpiece of double unit length between them) are caused to move sideways in an arcuate gap between the fluted cylindrical peripheral surface of a rotary drum-shaped wrapping conveyor or carrier and the complementary concave countersurface of a stationary block-shaped rolling device. The latter is provided with cutouts for the passage of pulsating beams issuing from two lasers and arranged to penetrate through adhesive-coated uniting bands which are convoluted around the filter mouthpieces and the adjacent portions od the respective plain cigarettes of unit length while these rod-shaped articles are caused to roll in the aforementioned gap. Each beam is caused to provide the uniting bands with pairs of perforations which are located diametrically opposite each other, and each pulsating beam is arranged to provide successive convoluted uniting bands with several pairs of perforations.
The width of the arcuate gap between the convex surface of the rotating drum-shaped wrapping conveyor and the concave surface of the stationary rolling device is less than the diameters of rod-shaped articles in the gap. This is necessary in order to ensure that the groups of coaxial articles are compelled to rotate in a predictable fashion about their common axis during travel through the gap, as well as to ensure predictable convoluting of the adhesive-coated uniting bands around the rod-shaped filter mouthpieces and the adjacent end portions of the respective plain cigarettes of unit length during conversion of such articles into filter cigarettes of double unit length. Thus, the wrapping conveyor and the block-shaped rolling device subject the rod-shaped articles in the gap to rather pronounced mechanical stresses which are apt to adversely affect the appearance and/or the quality of the ultimate products, especially in a modern filter cigarette maker wherein the rod-shaped articles in the gap must advance at a very high speed if the maker is to turn out desired quantities of filter cigarettes per unit of time.
Certain attempts to overcome the drawbacks of the just described machines, i.e., to reduce the stressing of the rod-shaped components and of the wrappers of filter cigarettes or analogous commodities, are disclosed in German patent No. 33 13 064 A1 which proposes to advance the cylindrical parts of the smokers' products in flutes provided in the cylindrical peripheral surface of a rotary drum-shaped conveyor. This conveyor is driven by a first hollow shaft which confines a part of a rotary second hollow shaft. One end portion of the second hollow shaft extends beyond the first hollow shaft and contains a beam divider arranged to direct beams of radiation against a mirror. Each of the just mentioned beam divider and mirror cooperates with a focussing lens, and these parts are confined in the aforementioned end portion of the second hollow shaft. The laser is located at the other ends of the hollow shafts and is arranged to furnish a pulsating beam which is caused to advance through the second hollow shaft and is split into two discrete beams before it reaches the rod-shaped components of the smokers' products. Such discrete beams advance through a slit, which is provided in one of the shafts, prior to impinging upon the exposed filter mouthpiece of a filter cigarette of unit length. The inner shaft is caused to rotate in the direction of rotation of the drum-shaped conveyor but at a higher speed; this is intended to ensure that the wrapper of each discrete filter cigarette is provided with several successive perforations during each revolution of the second (inner) hollow shaft.
A drawback of the just described proposal is that the apparatus which is disclosed in this German patent can be utilized only in conjunction with the treatment of filter cigarettes of unit length.
Similar drawbacks are exhibited by the apparatus which is disclosed in German patent No. 35 101 19 C2. This apparatus is designed to drill holes in the wrappers of cigarettes or the like. The patented apparatus employs a source of a laser beam which impinges upon a diffuser lens so that its components act upon (i.e., perforate) rod-shaped articles in discrete flutes turnably arranged on a drum-shaped conveyor for rod-shaped articles.